This invention relates generally to integrated gasification combined-cycle (IGCC) power generation systems, and more specifically to methods and apparatus for cooling gas turbine engine components in IGCC systems.
At least some known IGCC systems include a gasification system that is integrated with at least one power producing turbine system. For example, known gasifiers convert a mixture of fuel, air or oxygen, steam, and/or limestone into an output of partially combusted gas, sometimes referred to as “syngas”. The hot combustion gases are supplied to the combustor of a gas turbine engine, which powers a generator that supplies electrical power to a power grid. Exhaust from at least some known gas turbine engines is supplied to a heat recovery steam generator that generates steam for driving a steam turbine. Power generated by the steam turbine also drives an electrical generator that provides electrical power to the power grid.
At least some known gasification processes may generate flows of nitrogen. For example, an air separation unit used to generate and supply oxygen to the gasifier may generate oxygen by separating nitrogen and oxygen from a supply of air. Some of the nitrogen may be used to facilitate controlling emissions generated by the gas turbine engine. For example, nitrogen may be injected into the combustion zone of the gas turbine engine to reduce combustion temperatures, and to reduce nitrous oxide emissions from the gas turbine engine. However, even if some nitrogen is used for emissions control, some excess nitrogen may still be generated. Excess nitrogen is typically vented from known IGCC systems to the atmosphere.